Trouble with the Watchdog

I have a Dynamixel XW540-T260. Firmware is the latest (48). Running Protocol 2.0.

I’m having a problem with the watchdog timer when operating in Position mode or Current Based Position mode with a home offset.

Example situation: I`m in Current based position mode with a home offset. I set the watchdog timer (address 98) to 10 (200ms). Torque is on. Servo is responding normally to position commands.

But then I break communication (for example, pull the usb cable out of the computer) - the servo makes an “uncommanded” move and then stops. Torque stays on. If I re-establish communications, the error flag is -1 and has to be cleared.

So everything works as expected except for the “uncommanded” move before stopping. This is obviously very bad.

This same pattern happens in Position Mode or Current Based Position, but not in other modes, but I think a home offset has to be set for it to happen.

Am I just doing something wrong?


Bernard Despins

Hello Bernard,

Would you be able to perform a Firmware Recovery to ensure that your servo is properly running the latest v48 firmware.

This issue was officially logged as fixed in the v48 update, and during testing to replicate the issue here it’s only occurring after downgrades to lower firmware. If this error continues to occur following a firmware restoration, please let me know!

I did a Firmware recovery as you asked, but address 6 (firmware) said 48 before, and it still says 48 after.

Problem still occurs.

The situation that I can recreate any time is this:

Operating mode 5- current based position
Torque On
Command the servo to move position back and forth no problem.
Torque OFF
Set HomeOffset to -250
Set Watchdog to 1000 ms
Torque On
Command the servo to move position back and forth no problem.
Wait for the servo to be done all movement.
Pull the USB cable.
Servo does an un-commanded movement that seems to be equal to the homeoffset.

I’m wondering if anybody else can reproduce this problem with Firmware 48?



Is any support available for this?



We have confirmed that the issue reproduces in that firmware.
The manufacturer is waiting to distribute an improved program.
First, we will send you the improved program.
thank you

Thank you.

Appreciate it.